Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements ( pixels), each pixel is attached to a transistor and capacitor ''actively'' maintaining the pixel state while other pixels are being addressed, in contrast with the older passive matrix technology in which each pixel must maintain its state passively, without being driven by circuitry. Active matrix technology was invented by

Bernard J. Lechner Bernard J. Lechner (25 January 1932 – 11 April 2014) was an electronics engineer and formerly vice president, RCA Laboratories, where he worked for 30 years covering various aspects of television and information display technologies. Biogra ...

at RCA, using

MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

s (metal–oxide–semiconductor field-effect transistors). Active matrix technology was first demonstrated as a feasible device using thin-film transistors (TFTs) by

T. Peter Brody T. P. "Peter" Brody (18 April 1920 Budapest, Hungary – 18 September 2011 Pittsburgh, Pennsylvania, United States) was a British-naturalised physicist and the co-inventor of Active Matrix Thin-Film Transistor display technology together with F ...

, Fang Chen Luo and their team at the Thin-Film Devices department of Westinghouse Electric Corporation in 1974, and the term was introduced into the literature in 1975. Given an ''m'' × ''n'' matrix, the number of connectors needed to address the display is ''m'' + ''n'' (just like in passive matrix technology). Each pixel is attached to a switch-device, which ''actively'' maintains the pixel state while other pixels are being addressed, also preventing

crosstalk In electronics, crosstalk is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, induc ...

from inadvertently changing the state of an unaddressed pixel. The most common switching devices use TFTs, i.e. a

FET The field-effect transistor (FET) is a type of transistor that uses an electric field to control the flow of current in a semiconductor. FETs (JFETs or MOSFETs) are devices with three terminals: ''source'', ''gate'', and ''drain''. FETs contr ...

based on either the cheaper non-crystalline thin-film silicon (

a-Si Amorphous silicon (a-Si) is the non-crystalline form of silicon used for solar cells and thin-film transistors in LCDs. Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films onto ...

), polycrystalline silicon (

poly-Si Polycrystalline silicon, or multicrystalline silicon, also called polysilicon, poly-Si, or mc-Si, is a high purity, polycrystalline form of silicon, used as a raw material by the solar photovoltaic and electronics industry. Polysilicon is produ ...

), or CdSe semiconductor material. Another variant is to use diodes or resistors, but neither

diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

s (e.g. metal insulator metal diodes), nor non-linear voltage dependent

resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

s (i.e. varistors) are currently used with the latter not yet economical, compared to TFT. The Macintosh Portable (1989) was perhaps the first consumer laptop to employ an active matrix panel. Since the decline of cathode ray tubes as a consumer display technology, virtually all TVs, computer monitors and smartphone screens that use

LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...

or OLED technology employ active matrix technology.

References

{{Reflist Display technology

See also

References